Tin-based dual-modification enabling enhanced air stability and electrochemical performance for Li 5.5 PS 4.5 Cl 1.5 in all-solid-state lithium metal batteries

As one of sulfide electrolytes, chlorine-rich lithium argyrodites (Li 5.5 PS 4.5 Cl 1.5 ) have significant advantages as solid state electrolytes (SSEs) in all-solid-state batteries (ASSBs) due to their ultra-high conductivity. However, their practical application is limited by poor air stability and weak compatibility with Li metals. Herein, we enhance the performance of Li 5.5 PS 4.5 Cl 1.5 by doping it with SnO2, resulting in the formation of the Li 5.58 P 0.92 Sn 0.08 S 4.34 O 0.16 Cl 1.5 electrolyte. The introduction of Sn and O dopants forms strong Sn-S and P-O bonds in the electrolyte, replacing the sensitive P-S bonds and suppressing H2S release. Additionally, this doped electrolyte demonstrates an impressive Li-ion conductivity of 5.71 mS cm- 1 , a high critical current density of 2.9 mA cm- 2 , and significantly improved air and moisture stability. Moreover, the Sn dopant produces a Li-Sn alloy layer on the bare Li metal anode, endowing the ASSB with an initial discharge capacity of 146.7 mAh/g at 0.2C and a capacity retention of 86.2 % after 200 cycles at 0.5C. Combining with a 10 wt% SnF2-treated Li metal anode to further strengthen the electrode interfacial stability by the in-situ formed Li-Sn and LiF derivatives, the resultant full cell delivers a promoted initial discharge capacity of 179.5 mAh/g at 0.2C and a high discharge capacity of 112.2 mAh/g after 300 cycles at 0.5C. The dual strategy of electrolyte doping and Li anode modification achieves a synergistic effect that enables the ASSB to exhibit superior electrochemical performance, providing an effective way of preparing stable sulfide-based SSEs for large-scale applications.